Units …

I started with the MPG Illusion quiz at http://www.fuqua.duke.edu/news/mpg/mpg.html. 3/18 students guessed that upgrading the SUV was the better choice. (One asked “Why do 95% get the wrong answer?” which is a really good question. (Even though 3/18 isn’t 95%) That led later to noting that EPA now requires gallons/mile as well as well as miles/gallon on new car stickers.

After working the problem and surprising the class I introduced the “write down the units” mantra, pointing out that they could be cancelled algebraically. That means you can set the equations up without having to guess whether to multiply or divide.

Fortunately, several students were cheerful guinea pigs – willing to say they were confused, and willing to let me teach them while the rest of the class listened. I worked a currency conversion problem and was about to start on the cost of gasoline in Europe – so converting $/gallon to euros/liter. Never got there since one student asked for a solution to the SCOPE homework exercise on waiting for the light to change. One student volunteered her strategy – beginning with a web search for the length of a red light. I was initially skeptical, then realized that it was in fact a possible way to attack the problem, and followed through to the surprising conclusion that 6 months waiting in a lifetime was about 10 red lights per day.

Thursday I hope to work on stuff that will help them with the assignment due next Tuesday. That will go better if I can convince them to start today and tomorrow.

Signing off now – with the full understanding that this isn’t nearly as complete a report as Maura’s from the last class.

http://scope.math.umb.edu/exercise/238/waiting-for-the-light-to-change/

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